Centrifuge and method for using same



1956 .R. B. BENNETT ET AL CENTRIFUGE AND METHOD FOR USING SAME Filed 001:. 21, 1955 .INVENTORS. Guy E. Spencer. Rufus B. Bennett,

k E348 mmmviuma U kwkmwm w CE I- =l' UGE AND METHOD FUR USING SAlViE Application October 21, 1953, Serial No. 387,502

6 Claims. (Cl. 210-70) This application is directed to an improved centrifuge and method for using the same.

Objects and advantages of the present invention will be seen from the following description taken with the drawing in which Fig. l is an elevation partly in section showing an embodiment of the present invention;

Fig. 2 is a view taken along lines 22 of Fig. 1;

Fig. 3 is a fragmentary view taken along the lines 33 of Fig. 1; and

Fig. 4 is a fragmentary view showing a portion of the device of Figs. 1 and 2 on a larger scale.

Turning now specifically to the drawing, a basket type centrifuge consists of housing A with housing door B mounted thereon by a suitable hinge 11 and releasably secured thereto by catch 12. Mounted within housing A is perforated basket C which is carried on shaft D for rotation by a suitable prime mover E such as an electric motor. Solids from the centrifuge are discharged through chute F. A motor G is provided for vertically moving the chute F. Motor G is arranged to rotate a threaded shaft 13 which fits into a suitable threaded opening in mounting block 14 which, in turn, is secured to chute F by cap screws 15. Block 14 is also provided with openings 16 into which guide rods 17 slidably fit. Thus, the guide rods 17 and threaded shaft 13 which, in turn, are mounted on door B provide the mounting assembly to which chute F is secured.

A suitable charge stock is introduced through charge line 18 which passes through the wall of housing A and terminates in a spray head 19 which directs the introduced fluid against the centrifuge basket C. It is well known that the feed provided for a basket type centrifuge is a suspension of solids in liquids, the solids being retained by the basket as cake in the drawing, while the liquids pass through the basket and may be withdrawn from the lower part of the housing through outlet line 9.

The cake removing and discharging portion of the centrifuge consists of chute F mounted as previously described to be moved vertically by motor G. The lower end of chute F fits as a slip joint into passage 21 mounted on the lower portion of door B, said passage extending below as an outlet 22 which makes a friction fit with the upper end of a discharge line 23. Mounted on the top of chute F is a knife member 24 having an edge coextensive in width with the width of the filter cake on the basket for removing cake uniformly, said blade terminating in a knife edge 25, which is vertically above the mouth of chute F.

In order to prevent the cake being removed by the knife edge 25 from clogging up the chute F, the assembly H is provided. Assembly H consists of a plurality of nozzles 30 mounted in a row on knife member 24 parallel with knife edge 25 with each nozzle 30 connected through a line 31 to manifold 32 which, in turn, is connected to nited States Patent a flexible hose or line 33 for supplying the liquid to be jetted through nozzles 30.

Nozzles 30 are mounted on blade 24 so that the streams projected or jetted therefrom enter the discharge chute F and strike a wall thereof without any substantial amount of liquid splattering out of the discharge chute. The streams from nozzles 30 form a liquid curtain across the vertical path of travel of the portions of filter cake removed by knife edge 25 at a point above the mouth of chute F. This prevents the cake removed from the centrifuge basket C from bridging the clogging up the chute.

By way of example, a basket type centrifuge with a basket 3 feet in diameter and 1 foot wide, with a knife member also 1 foot wide, was provided with 4 equidistantly spaced nozzles with their discharge side flush with the side of the knife and about 3 /2 inches below the knife member, said jets being directed into the mouth of the discharge chute of the centrifuge and making an angle of 30 with the horizontal.

As another example in a basket type centrifuge with a basket 18 inches in diameter and 2 /2 inches in width, the knife member also 2 /2 inches wide was provided with three equidistantly spaced jets about 2 /2 inches below the knife blade and a fourth jet about 5 inches below the knife blade, all of said jets being directed into the mouth of the discharge chute of the centrifuge and making an angle of 30 with the horizontal. This centrifuge was used for separating paraxylene crystals both before the nozzles were mounted to the knife and after the nozzles were applied. In the batchwise operation a cake was built up to a 1 /2 thickness after which the feed was cut off and the cake then removed by a knife blade a total of 4 seconds being used to remove the cake. Without the use of said nozzles 30, the chute became plugged up severely in a time ranging from 30 minutes to one hour. By the application of the present invention wherein nozzles 30 were mounted on the knife member and melted paraxylene product was recycled through line 33 and injected through nozzles 30 all plugging of the discharge chute was eliminated. It was found desirable to maintain the liquid passed through the jets at a temperature between F. and F. with a minimum of seven parts of liquid through the jets to three parts of solids from the filter cake.

The operation as described has been found to have considerable advantages. The jetting of liquid into the crystals above the mouth of the discharge chute not only prevents plugging of the discharge chute in the centrifuge itself, but in addition allows the product to be readily handled so that in a plant employing four basket type centrifuges a single product tank is sufiicient in contrast to the requirement of a separate melt tank per each centrifuge when the present invention is not employed.

Having fully described and illustrated the present invention, what is desired to be claimed and securedby Letters Patent is:

1. In a basket type centrifuge having a cylindrical perforate basket mounted for rotation about a horizontal axis, a downwardly extending discharge chute with its upper end open, mounting means arranged for moving said chute vertically, a flat knife member with its free end terminating in a knife edge carried by the upper end of the chute with the knife edge spaced vertically above the opening of the chute whereby cake removed from said centrifuge basket by said knife edge may drop downwardly in a vertical path of travel into the upper open end of said chute, a plurality of nozzles mechanically linked to said chute for vertical movement therewith and connected to the knife member for discharging below the knife edge, said nozzles being arranged to direct streams of liquid into said chute and against a wall thereof and forming a liquid curtain across the path of fall of the filter cake above the open end of said chute.

2. A device in accordance with claim 1 in which said nozzles extend through openings in the knife member from a first side to a second side and are secured to said knife member with the discharge ends of the nozzles substantially flush with said second side.

3. A device in accordance with claim 2 in which said nozzles make an angle of approximately 30 with the horizontal.

4. A device in accordance with claim 1 in which said nozzles make an angle of approximately 30 with the horizontal.

5. A method for separating meltable crystals from mother liquor in which an annularly shaped filter cake is formed on a cylindrical surface, the method of removing said filter cake to an open mouthed, downwardly extending discharge chute which comprises, removing portions of said filter cake from said filter surface, causing said removed portion of filter cake to fall along a vertical path of travel such that they will pass into the mouth of said discharge chute, forming a liquid stream having the same composition as the filter cake, and jetting said stream into said discharge chute at such an angle as to avoid splattering out of said chute to form a liquid curtain across the mouth of said discharge chute.

6. A method in accordance with claim 5 in which the meltable crystals are paraxylene and the jetted liquid stream is at a temperature in the range between 75 and 100 F. with a minimum ratio of 7 parts of liquid to 3 parts of crystals.

References Cited in the file of this patent UNITED STATES PATENTS 756,342 Dulin Apr. 5, 1904 958,068 Arbuckle May 7, 1910 1,012,974 Bird Dec. 26, 1911 1,217,207 North Feb. 27, 1917 1,512,977 Depue Oct. 28, 1924 2,056,885 Pecker Oct. 6, 1936 2,268,788 Wanner et al. Jan. 6, 1942 2,614,134 Powers Oct. 14, 1952 2,658,620 Davis et a1 Nov. 10, 1953 

1. IN A BASKET TYPE CENTRIFUGE HAVING A CYLINDRICAL PERFORATE BASKET MOUNTED FOR ROTATION ABOUT A HORIZONTAL AXIS, A DOWNWARDLY EXTENDING DISCHARGE CHUTE WITH ITS UPPER END OPEN, MOUNTING MEANS ARRANGED FOR MOVING SAID CHUTE VERTICALLY, A FLAT KNIFE MEMBER WITH ITS FREE END TERMINATING IN A KNIFE EDGE CARRIED BY THE UPPER END OF THE CHUTE WITH THE KNIFE EDGE SPACED VERTICALLY ABOVE THE OPENING OF THE CHUTE WHEREBY CAKE REMOVED FROM SAID CENTRIFUGE BASKET BY SAID KNIFE EDGE MAY DROP DOWNWARDLY IN A VERTICAL PATH OF TRAVEL INTO THE UPPER OPEN END OF SAID CHUTE, A PLURALITY OF NOZZLES MECHANICALLY LINKED TO SAID CHUTE FOR VERTICAL MOVEMENT THEREWITH AND CONNECTED TO THE KNIFE MEMBER FOR DISCHARGING BELOW THE KNIFE EDGE, SAID NOZZLES BEING ARRANGED TO DIRECT STREAMS OF LIQUID INTO SAID CHUTE AND AGAINST A WALL THEREOF AND FORMING A LIQUID CURTAIN ACROSS THE PATH OF FALL OF THE FILTER CAKE ABOVE THE OPEN END OF SAID CHUTE. 